Abstract
Human societies greatly depend on tools, which spare us considerable time and effort. Humans might have evolved a bias to employ tools, using them even when they are unnecessary. This study aimed to investigate whether adult humans and a distantly related habitually tool-using vertebrate species, the New Caledonian crow (Corvus moneduloides), use tools depending on their necessity. In addition, children aged 3 to 5 years were examined to investigate the developmental pattern. The task involved choosing between using a body part (i.e. crows: beak; humans: hand) or a tool for retrieving a reward from a box. All subjects were tested in two conditions. In the Body+/Tool− condition, using the body was more efficient than using the tool, and conversely in the Body−/Tool+ condition. Our results suggest that the capacity to employ tools economically develops late in humans. Crows, however, failed to choose economically. At the individual level, some subjects exhibited striking individual preferences for either using a tool or their beak throughout the task. Whether such biases depend on individual experience or whether they are genetically determined remains to be investigated. Our findings provide new insights about tool use and its cognitive implementation in two outstanding tool-using taxa.
Highlights
Studies involving patients with neuropsychological syndromes have significantly contributed to a better understanding of human tool-related cognition[6,7,8]
When using the hand was slightly more beneficial than using the tool, subjects preferred to use a tool to solve the task. These results suggest that adult humans do not always behave economically when using a tool
It serves as indirect evidence that by the age of 4, children may either lack the ability to estimate the benefits provided by tool use accurately or they might be biased to interact with tools
Summary
Studies involving patients with neuropsychological syndromes (e.g. apraxia: a disorder of learned gestures, in the absence of sensory or motor deficits5) have significantly contributed to a better understanding of human tool-related cognition[6,7,8]. Adult humans perceive a distant target closer when they intend to reach it with a tool rather than with the hand, and this occurs when the subject passively observes a tool-use action made by another individual[15,16]. When using the hand was slightly more beneficial than using the tool, subjects preferred to use a tool to solve the task These results suggest that adult humans do not always behave economically when using a tool. A tendency to overestimate the benefits conferred by tool use probably through social and asocial learning, but possibly including some genetic factors This propensity, gets masked the more conspicuous the difference in terms of time and effort between using the tool and using the hand becomes[19]. It serves as indirect evidence that by the age of 4, children may either lack the ability to estimate the benefits provided by tool use accurately or they might be biased to interact with tools
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